In an up-link in the E-UTRA system, which is currently standardized, in 3GPP (3rd Generation Partnership Project), it is now under consideration to time-multiplex pilot signals and data or control signals within a frame in unit transmission time, as described in the non-patent document 1. In the following explanation, “data” means “data or control signal” for brief description.
The pilot signal is used, for example, for channel estimation necessary for data demodulation. Moreover, even when data is not transmitted, the pilot signal is used for channel quality measurement used for scheduling or adaptive modulation. In the field for a pilot signal (hereinafter referred to as a pilot field), shown roughly in FIG. 1, it has been studied to multiplex pilot signals of plural mobile stations in such that a mobile station, which does not transmit data in the frame, can transmit the pilot signal. The mobile station transmits a pilot signal according to a predetermined period and radio resource, previously specified, without depending on data transmission. By doing so, the base station can measure the quality (SIR: Signal to Interference Ratio) of the channel between the base station and mobile stations which do not transmit data. The base station uses the channel quality information to calculate scheduling index or to determine MCS (Modulation and Coding Set) in adaptive modulation.
However, the EUTRA system may synchronize the transmission timing loosely between neighboring base stations. In such a case, the base station receives the pilot signal transmitted from a mobile station within its self-cell and a pilot signal transmitted from a mobile station within other cell, with the same timing. For that reason, SIR measured with the pilot signals is measured as interference a pilot signal power transmitted from a mobile station linked to a neighboring cell (see FIG. 2).
As described above, since the pilot signal is transmitted in a predetermined period independently without depending on data transmission, an interference-by-other cell component of SIR measured in a pilot field does not match with an interference-by-other cell component received in the field for data (hereinafter referred to as data field). That is, the correlation between SIR measured in the pilot field and SIR measured in the data field becomes, small.    Non-patent document 1: TR25.814v7.0.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved UTRA (Release 7)